The present invention relates to abrasives for use in chemical mechanical polishing, in particular, the polishing of metal or dielectric layers that may be formed when making semiconductor devices.
Semiconductor devices may include a shallow trench isolation region and several metal layers that are separated by dielectric layers. As that region and those layers are formed, it may be necessary to remove from the device excess metal or dielectric material. A chemical mechanical polishing process is commonly used to perform that function. In such a process, a slurry may be dispensed onto a polishing pad to facilitate removal of the excess material.
Although a slurry""s composition may differ depending upon the type of material that is removed during the polishing operation, it generally will include an abrasive. For the chemical mechanical polishing of metal or dielectric material, two forms of silica abrasive are commonly usedxe2x80x94i.e., fumed silica and colloidal silica. Fumed silica may, for example, be used when polishing the dielectric material that forms the device""s shallow trench isolation region. Colloidal silica may be used when polishing barrier layers, e.g., those comprising tantalum. In general, fumed silica enables a high polish rate, but exhibits poor defect performance, while using colloidal silica may limit defects, but may also reduce the polishing rate.
In many applications, however, both a high polish rate and good defect performance are desired. Accordingly, there is a need for an abrasive that facilitates a high polish rate while providing satisfactory defect performance. The composition of the present invention provides such an abrasive.